Device and method for detection/indication of liquid leakage

ABSTRACT

An improved device for the detection of leakage is achieved when the device includes at least two components, of which at least one is capable of migrating with the liquid within the carrier, and forming a distinct color or other detectable signal with the first component. Such device is not sensitive to normal, ambient humidity and the color signal formed is resistant to being diluted or rinsed away in cases of abundant or repeated leakage.

TECHNICAL FIELD

The present invention concerns a device and a method for the detectionand/or indication of liquid leakage, sensitive already to droplets andsmall amounts of liquids.

BACKGROUND OF THE INVENTION

The leakage of liquids, and in particular stealthy leakage, can occur inapartments and houses, as well as in other real estate and cause seriousdamage, requiring expensive reparations. It is not unusual that minorleaks occur in or around valves in both old and modern hot waterradiators when the liquid flow is adjusted, or when the radiator isaired that is the top valve is opened in order to remove entrapped air.Leakages in pipe joints, couplings and fittings for example to householdappliances, such as dish washers and washing machines, may be difficultto detect, in particular when built in or hidden.

A leak can take the form of drops, droplets, or a fine spray or mist ofliquids. A leak can also occur in the form of a liquid film, spreadingalong a pipe. Even the condensation of liquid on a cold water pipe cancause damage. It frequently happens that such minor leaks/condensationis not discovered until the secondary damage becomes apparent. At thatstage, the extent of reparations necessary will also become greater andthus more expensive.

Various devices for the detection of leakage are known. U.S. Pat. No.6,128,947 describes a gasket or apron having a colorant-emitting discattached thereto, the colorant in said disc being released by contactwith water. This disc is however intended to be permanently mountedunder a toilet, and cannot be held to be easily installed or removed.

DE 4 105 044 describes a method for testing the leak-tightness of apipe, either by holding the pipe at a slight vacuum or over-pressure anddetecting changes in this vacuum or pressure, or by observing a pigmentlayer surrounding the pipe, which pigment reacts with an indicatorsubstance emitted from said pipe.

U.S. Pat. No. 3,485,085 describes a method for detecting leaks in thecooling system of a power reactor, wherein an apertured container isplaced around a point where leakage may occur, and a tape whoseresistivity changes on exposure to moisture is placed over the apertureof said container, and changes in the resistivity determined.

GB 2307558 describes a thin covering to be applied to pipe linesconveying a liquid medium, such as for example fuel, wherein saidcovering consists of a material which reacts in a chemical-physicalmanner with the liquid, producing a colour change.

U.S. Pat. No. 2,601,840 describes a leakage indicating cover for pipeflanges and valves, wherein said cover has a fabric lining impregnatedwith a chemical which changes colour when contacted by an acid or base.Among the examples mentioned are thymol blue, methyl red,phenolphthalein and litmus.

WO 94/02772 describes a method for leak detection where a film of colourchange material is formed on the outer surface of a liquid-carryinghose, where the material will react with possible escaping liquid toprovide a visible indication. The colour change material is completelyencapsulated in a protective film, and preferably applied to the hose byspraying.

JP 61250535 describes a tape for detecting leakage of water, whereinsaid tape is printed, coated or impregnated with a water-solublecolouring material, which becomes blotted upon contact with water.

Regardless of the considerable amount of prior art in this field, itappears that there still remains a need for a simple, inexpensive andeasily applicable device, as well as a simple and reliable method forthe detection of minute amounts of liquid or stealthy leakage. Oneobjective of the present invention is to make available such a device,which is easily placed at the site of a suspected leak, easily removedand replaced. Another objective is to ensure that the device and methodare reliable also when the leakage is abundant, i.e. that the indicatorsubstance is not rinsed away or diluted to an extent that the colourindicating leakage becomes unrecognisable.

A further objective is that the device and method are not influenced byambient humidity. Further objectives and the corresponding features ofthe invention, as well as the advantages thereof, will become apparentto a skilled person upon a closer study of the description and examples.

SUMMARY OF THE INVENTION

The above objectives are met by a device comprising a carrier permeableto said liquid, and at least two components, whereof at least one iscapable of migrating within the carrier when the carrier is wetted bysaid liquid, the components or parts thereof forming a coloured complex,which coloured complex is not diluted or significantly changed by asurplus of said liquid, or which remains immobilised to the carrier.

The invention is further defined in the attached claims, incorporatedherein by reference.

SHORT DESCRIPTION OF THE DRAWINGS

The present invention will be described in closer detail below, in thedescription, examples and claims, with reference to the attached figuresin which:

FIG. 1 shows (a) how two components are present in the carrier material;(b) how the presence of a liquid dislocates or dissolves, eitherentirely or partially, both components, bringing them together forming acoloured complex; and (c) how the coloured complex is visible whereasnone or only minor amounts of the components remain.

FIG. 2 shows (a) how two components are present in the carrier material;(b) how the presence of a liquid dislocates one of the components butnot the other; and (c) how a complex is formed, indicating that thecarrier has been subjected to a liquid.

FIG. 3 shows one embodiment of the invention where the device is shapedas a substantially rectangular sheet, having perforations making itsuitable for affixing to pipes of different diameter.

FIG. 4 shows another embodiment, where the device is delivered as acontinuous elongated shape, preferably in the form of a roll, where theindividual indicator devices are separated by perforations.

DESCRIPTION

In the context of the present invention, the term “liquid” encompassesboth aqueous liquids and non-aqueous liquids, such as water, solvents,fuels, heat-transfer solutions etc.

The terms “component” and “components” are here used to define thecomponents in a couple of at least two compounds, distributed in thecarrier, which are capable of reacting with each other in the presenceof a liquid, and forming a detectable, stable reaction product. The term“stable” means that the reaction product is non-soluble in said liquid.The term “detectable” means that the reaction product has a property,e.g. a colour, which is detectable, preferably detectable by the unaidedeye. Alternatively, the colour is detectable or accentuated whensubjected to light of a certain wavelength, e.g. ultraviolet light.

The terms “carrier” and “carrier material” are here used to define aporous material which is wettable by the liquid to be detected, andcapable of retaining and presenting a detectable, stable reactionproduct. The exact structure composition and colour of the carrierdepend on product. If the reaction product is a coloured complex, thecarrier preferably has a light or neutral colour, and most preferably acolour aiding in the identification of the coloured complex. Further,the combination of carrier material and components should be such thatsaid coloured complex is detectable regardless if the carrier is wet ordry, that is penetrated by the liquid or not.

The carrier material can be a more or less structured fibrous material.Examples include paper, which is here held to represent a lessstructured fibrous material, and thread, yarn, braided threads or yarns,cloth, tissue or fabric, the latter being held to represent a morestructured fibrous material. Examples of fibres include natural fibres,such as cellulose and mineral fibres, and synthetic fibres, such aspolymer fibres. The main concern is that the carrier can be wetted orpenetrated by the liquid to be detected, and that diffusion of saidliquid within the material is possible.

The carrier can also be in the form of a foamlike material, or a gel,provided that said foam or gel is suitable for application, that isfulfils the necessary physical requirements, and is sufficiently porousto the liquid to be detected.

Said physical requirements mean that the carrier should be capable ofbeing attached to the site where leaks are to be detected, for examplebelow a valve, around a pipe etc. When the carrier material is afoamlike material or a gel, it is conceived that it is furtherreinforced with fibers.

When the resulting reaction product, the coloured complex, although itis non-soluble in the liquid to be detected, may be prone to move withinthe carrier through the action of said liquid. This may in particular bethe case when the coloured complex forms very small particles, forexample a sol or a colloidal solution. A particular aspect of theinvention is thus the use of a more dense fibrous or porous structure,or the combination of a dense structure and an immobilising agent.

Another aspect of the invention is that the physical dislocation of thecomponents from the carrier is prevented through the use of a substance,which immobilises at least one of the components and the resultingreaction product in the carrier. One example of such substance aresuitable glues, another example is the use of a gel-forming agent in thecarrier.

One aspect of the invention is an improved method and device for thedetection of leakage, which is achieved when a device is used, saiddevice comprising at least two components, the first of which isimmobilised in a carrier, while the second migrates with the liquid andforms a distinct colour or other detectable signal with said firstcomponent Such device is not sensitive to normal, ambient humidity andsignal formed is resistant to being diluted or rinsed away in cases ofabundant or repeated leakage.

When selecting the components, it is preferred that they fulfil thefollowing requirements:

-   -   Primarily only fluids in liquid form are detected. Ambient        humidity does not result in the formation of a coloured complex.    -   The coloured complex is stable and does preferably neither fade        nor dissociate in light or in dryness.    -   The coloured complex is preferably non-soluble in the liquid to        be detected.    -   The toxicity of the components should be sufficiently low,        considering the concentrations used, that the device does not        constitute a health hazard, in particular to children or pets.    -   A non-stoichiometric mixture of the components is preferred,        when applicable.    -   The un-reacted components as such are preferably non-coloured or        have only little colour, or a colour which can be masked or        neutralised by the colour of the carrier.

According to one embodiment of the invention the device is asubstantially rectangular sheet of a carrier material, comprising thenecessary components. FIG. 2 shows an embodiment where the device is asubstantially two-dimensional sheet optionally carrying printedinformation, and having cut-outs or preferably concentric perforationsmaking it easily adaptable for use on pipes of different diameter. Thedevice may be cut or punched or delivered in the form of a larger sheetwith perforations separating individual devices, or as a tape or band,perforated at regular intervals or possible to cut or tear at desiredintervals. FIG. 4 shows an embodiment where the device is delivered inthe form of a tape or band, the individual devices separated byperforations.

Further, the device may be delivered in the form of a thread, a yarn, abraid, a band, or a sheet of said porous carrier material. The devicemay also be delivered in the form of sheets, cut or otherwise adapted bythe end-user with respect to the intended place of use.

According to a preferred embodiment, the device is in itself capable ofbeing affixed to a pipe, e.g by being shaped as a cylinder, a spiral ora sheet having an opening. The device may further comprise fasteningmeans, such as threads, elastic bands, metal clips or strips, adhesivepatches, tape etc. Said fastening means may either be an integrated partof the device, or supplied separately, and used to affix the device at adesired location. It is conceived that alternative fastening means aresupplied with each device, so that the end-user can choose the fasteningmeans best suited for the location.

The method according to the invention is mainly a method for thedetection of leaks and in particular stealthy leaks at locations wherethere is a risk of leaks or unwanted condensation, such as on radiators,heat exchange elements, pipes and pipe joints, valves, couplings andfittings for example to household appliances, such as dish washers andwashing machines, regardless if these are permanent or temporaryinstallations. The method according to the invention is suitable bothfor use in private homes, public spaces, such as office spaces,hospitals and in industry.

The method comprises the steps of affixing a device capable ofindicating a liquid, in particular a device as defined in the presentdescription and claims, to a location where leak or condensation couldbe expected, followed by visual inspection of said device at regular orirregular intervals, wherein a colour signal is taken as an indicationthat a leak or condensation is taking place or has taken place.

The present invention has a considerable advantage in that the reactionproduct remains immobilised in the carrier, even if the device would besubjected to an excess of liquid. The inventive device and method haveanother advantage in that they indicate leaks without being sensitive toambient humidity, or aggregated humidity. The device is in other wordsbasically maintenance free and reliable. The inventive device mainlydetects leaks in the form of drops, droplets or aerosols. The inventivedevice has an advantage in being simple and easy to use, as well asinexpensive to manufacture. As the device is inexpensive, it becomespossible to use more frequently and with greater coverage, and not onlyfor random tests.

The inventive method and device make it possible to easily detect andindicate leaks already at an early stage, before more serious damage hasoccurred. The method and device is independent of external energy andsafe and easy to use and to read. These features and advantages make thedevice and method suitable for both professional and private use, whichby itself is an additional advantage of the invention. Further featuresand advantages of the invention will become evident to a skilled personupon study of the description, examples and figures.

EXAMPLE

The device and method will now be presented in the form of an example,said example focussing on simple ionic reactions, as this constitutes apreferred embodiment of the invention, in particular when the device andmethod is intended for the detection of aqueous liquids. An importantconsideration in this embodiment is that the transport of thecomponents, necessary for the indicative reaction to start, only takesplace when the device is wetted by the liquid to be detected, and thatthe reaction does not start as long as the device remains dry.

The device according to the invention comprises a porous carrier withparticulate grains of the colourless compounds “AB” and “CD”. The grainsare evenly distributed in the carrier and unable to react with eachother as long as the carrier remains dry. In FIG. 1( a) this isillustrated by the hexagonal shape and the triangular shape, symbolizingsuch grains. When the carrier is wetted, as shown in FIG. 1( b) thecompounds are dissolved or dislocated, forming a coloured complex.

In FIG. 2( a) the two components are illustrated by an unfilled squareand a filled hexagonal shape, the square symbolizing a componentimmobilised to the carrier. When the carrier is wetted, as shown in FIG.2( b) the compounds are dissolved, where applicable, and such compoundsnot immobilised to the carrier will migrate in the carrier. In FIG. 2(c) the two components have reacted, forming a coloured complex.

According to one embodiment, the components may dissociate into ions asschematically shown below:AB=>A ⁺ +B and CD=>C ⁺ +D ⁻

The ions may now migrate within the carrier and result in the followingreaction:A ⁺ +D ⁻ =>AD (coloured complex)

Here, AD is preferably a non-soluble or only sparingly soluble complexwith a distinct colour which is not diluted or rinsed away even in thepresence of a surplus of the liquid to be detected.

In FIGS. 1( b) and (c) this is illustrated by the unfilled squaresrepresenting a compound immobilised to the carrier, and the filledhexagonal shapes representing the compound or part of a compound whichmigrates in the carrier.

It is also possible that a first component is very easily soluble, andthat this migrates in the carrier and forms a layer around a secondimmobilised or more slowly migrating component.

The following components are possible to use when the liquid to bedetected is water, an aqueous solution, a polar solution or a weaklypolar solution.

Components forming ferro and ferricyanate complexes, as these havestrong, distinct colours. Trivalent iron ions result in strong bluecolour in ferrocyanate complexes, whereas divalent ions give the sameresult in ferricyanate complexes. The first alternative is howeverpreferable, as ferrocyanates are both more stable and less toxic thanferricyanates.

One disadvantage of the above components is that the coloured complexmay form a colloidal solution, resulting in that the pigment whilenon-soluble, still may be diluted or rinsed out from the carrier.Measures preventing this must be taken, such as the addition of agelling substance.

Further examples of components are potassium ferrocyanate(K₄Fe(CN)₆.3H₂O and iron phosphate (FePO₄.2H₂O). These are preferred, asthe iron phosphate is rather sparingly soluble in water, resulting inthat it will be the ferrocyanate that migrates towards the phosphate,and the coloured complex (blue) will form a layer or shell around theiron phosphate, resulting in a blue/green color.

If a salt of divalent iron ions is used in combination with aferricyanate, it is preferred that the carrier material of the indicatordevice holds a surplus of divalent iron ions which then act as anantidote against the more toxic ferricyanate. This is an example ofnon-stoichiometric proportions of the components, adapted to compensatefor their toxic or other properties. This principle is naturallyapplicable also to other components.

Another preferred reaction is that between divalent cupper ions andferricyanate. This results in a strong reddish-brown complex of cupperferrocyanate which appears to be resistant to water. In this case, asurplus of ferrocyanate may be added as an antidote against the toxiccupper ions.

It should be added that it often is sufficient to use very low componentconcentrations in the carrier in order to achieve distinct colours. Theabovementioned non-stoichiometric considerations can then be resorted toas a safety precaution or if required by an official agency, such as theagency for occupational health.

Further, the choice of indicating reaction and consequently thecomponents, is governed by the intended use of the device, including theplace of use, the liquid to be detected, and the persons authorized touse the device. It is possible that one set of components becomeapproved for industrial use, whereas another set becomes approved forprivate use.

Although the invention has been described with regard to its preferredembodiments, which constitute the best mode presently known to theinventors, it should be understood that various changes andmodifications as would be obvious to one having the ordinary skill inthis art may be made without departing from the scope of the inventionwhich is set forth in the claims appended hereto.

1. A nontoxic device for detecting leakage of a liquid, comprising: acarrier permeable to the liquid; at least two components that aresoluble in the liquid, the components or parts thereof forming a coloredcomplex, which color is not significantly altered or removed by asurplus of the liquid, wherein said at least two components comprise afirst component which is immobilised to the carrier and a secondcomponent that migrates within the carrier when the carrier is wetted bythe liquid, the colored complex being immobilised to the carrier,wherein the first component comprises iron phosphate (FePO₄.2H₂O) andthe second component comprises potassium ferrocyanate (K₄Fe(CN)₆.3H₂O).2. Method for the detection of leakage of a liquid at a particularlocation, comprising providing the device according to claim 1 is placedin said location.
 3. A device according to claim 1, wherein the liquidto be detected is water.
 4. A device according to claim 1, wherein thecarrier is a porous material chosen among paper, thread, yarn, braidedthreads or yarns, cloth, tissue or fabric, foam materials, and gels. 5.A device according to claim 1, wherein said device has a substantiallytwo dimensional form chosen among a tape, a string, a braid, a ribbon, astrip, and a sheet.
 6. A device according to claim 1, wherein saiddevice is shaped as a sheet having concentric perforations foraccommodating pipes of different diameters.
 7. A device according toclaim 1, wherein said device further carries written information.
 8. Anon-toxic method for detecting leakage of a liquid, comprising the stepsof: providing a carrier permeable to the liquid, the carrier comprisingat least two components, the components or parts thereof forming acolored complex, which color is not significantly diluted or removed bya surplus of the liquid; affixing the carrier to a location whereleakage can be expected; and observing the carrier for color changes,wherein said at least two components comprise a first component which isimmobilised to the carrier and a second component that migrates withinthe carrier when the carrier is wetted by said liquid, the coloredcomplex being immobilised to the carrier, wherein the first componentcomprises iron phosphate (FePO₄.2H₂O) and the second component comprisespotassium ferrocyanate (K₄Fe(CN)₆.3H₂O).